Circuit control means



Oct. 4, 1932. D TAYLOR 1,880,524

CIRCUIT CONTROL MEANS Filed July 1931 2 Sheets-Sheet l 60/ UK AINVENTO/E D N/EL 6. TAYLOR M MM 4 rro/elvzvs Uct. 4, 1932. D. G. TAYLQR1,880,524

CIRCUIT CONTROL MEANS Filed July 15, 1951 2 Sheets-Shem 2 IN vz/v ToeKAN/EL 6. TA YL OE I .4 7-702 NEYS Patented Oct. 4, 1932 UNITED STATESPATENT OFFICE I DANIEL G. TAYLOR, OI MINNEAZPOIIIS, MINNESOTA, ASSIGNORTO MINNEAPOLIS- HONEYWELL BEG'ULATQB COMPANY, OF MINNEAPOLIS, MINNESOTA,A CORPORA- TION OF DELAWARE CIRCUIT CONTROL MEANS Application fled July15, 1931.

My invention relates generally to the control of electrical circuits andmore particularly to control systems utilizing a member movable underthe influence of a magnetic field or flux to effect the desired control.

In a simple ty e of control system, a movable control mem r is arrangedto open and close the energizing circuit of a relay whose armaturecontrols some other circuit by means of a switch or the like connectedthereto. The control member carries a contact for engagement with asecond contact and the arrangement is such that when these contacts areclosed the energizing circuit for the relay is closed and vice versa.When the contacts are very near the breaking point any slight vibrationmay thus cause interruptions in the energizing circuit for the relaythereby to open and close the same to its own detriment as well as thatof the contacts. The action of the relay under such conditions iscommonly called chattering.

In order to eliminate relay chattering, it has been proposed to providethe control member with two contacts adapted to engage successively withtwo other contacts. The proposed arrangement is such that one pair firstcloses and the other pair subsequently closes while the first remainsclosed, upon movement of the control member in one direction. When thecontrol member moves in reverse direction the second pair opens firstand the first pair opens subsequently. Upon initial closing ofthe firstpair of contacts no circuit will be closed but the closing of the secondpair will set up a circuit for initially energizing the relay. Thearmature of the relay Wlll then close a switch setting up a relayholding circuit through the first pair of contacts. As a result therelay remains energized after the second pair of contacts separate. Theinstant the firstpair separate, however, the holding circuit will bebroken so that the relay will be deenergized and its armature will moveto open the switch in the holding circuit. Any vibration between thefirst pair of contacts will not result in chattering since the relayenergizin circuit cannot again be closed after the rst pair of contactsonce separate,

Serial No. 550,932.

until the second pair of contacts again engage. The result is obtainedby so arranging the control that the control member deenergizes therelay at a different point in its path of travel from that at which itwas energized. Thus, a vibration ofthe contacts either at the point ofde-energization or the point of initial energization would not result ina making and breaking of the relay energizing circuit.

This proposed arrangement has the disadvantage that it depends foroperation upon the making of electrical connection between two pairs ofcontacts. If the first pair becomes corroded or fails to make properconnection for any other reason,the relay energizing circu't will makeand break upon vibration between the second pair of con tacts. If thesecond pair fails to make proper connection, the relay will never becomeenergized. It is a general object of this invention to provide a relaycontrol arrangement which will preclude possibilty of relay chatteringand which depends for operation upon only a single'pair of contacts.

A further object of the invention is the provision of a thermallyresponsive relay control device which requires only. a single pair ofcontacts to open and close a relay energizing circuit without permittingchattering.

Another object of the invention is the provision of a thermallycontrolled time switch for periodically energizing and (lo-energizing arelay, which likewise requires only a single pair of contacts foropening and closing the relay circuit without permitting chattering.

These and various other objects of'the invention will become morereadily apparent upon a detailed study of the accompanying drawings andspecification, together with the appended claims.

In the drawings, Fig. l is a diagrammatic showing of a previouslyproposed relay control arrangement which prevents relay chatter butwhich depends for operation upon two pairs of contacts;

Fig. 2 is a diagram illustrating a simple application of this inventionto the automatic control of a relay in response to ambient temperatureconditions;

Fig. 3 is a diagrammatic showing of an application of the presentinvention to a thermally responsive time switch for periodically openingand closing a relay circuit; and

Fig. 4 is a side elevation of the apparatus used in connection with themodification illustrated in Fig. 3.

According to the invention, each of the contacts for initially closingthe relay energizing circuit is carried on a separate movable member.These members are brought together into predetermined relative positionsto close the contacts and thereby energize the relay. Upon resultingmovement of the armature, a force is exerted upon one of the memberscarrying the contacts in the direction of its co-acting member so thatthe contacts will separate when their carrying members are in differentpositions from those occupied when the contacts closed. When thecontacts do separate the relay will be de-energized, the armature willmove back to relieve the force it exerted upon one of the contactcarriers, and that carrier will consequently shift its position awayfrom its adjoining one. As a result there will be no possibility ofvibration between the contacts after the relay has once beende-energized. So also, there will be no possibility of vibration uponinitial energization of the relay for upon first closing of the contactsthey will immediately be drawn more tightly together due to the forceexerted by the relay armature and will not be able to separate untilthey assume relative positions diflerent from those when the contactsfirst closed.

The carrier upon which the force is exerted by the armature is-preferablformed of resilient material so that it Will return to its normalposition when the force is relieved but this carrier may if desired bepivoted so as to return to normal position under the infiuence ofgravity or some equivalent means.

In a particularly advantageous application of the invention at least oneof the carriers is a thermostatic element. If desired, both carriers maybe thermally responsive as in the case of a thermally controlled timeswitch in which changes in ambient temperature are to be compensatedfor.

Referring to Fig. 1, which shows a known arrangement for eliminatingchattering, 2 designates a thermostatic element, preferably of thebi-metallic type, which carries a contact 3 for engagement with fixedcontact 4, and a contact 6 for engagement with fixed contact 8. Thearran ement is such that upon movement of the t ermostat to the left ofthe position shown, contacts 3 and 4 W111 first engage and then contacts6 and 8 will close while contacts 3 and 4 remain closed. Upon reversemovement to the right, contacts 6 and 8 will first open and contacts 3and 4 will subsequently open. The relay coil 10 has an armature 12 whichmoves to the right when the relay is de-energized. Upon enerization, thearmature moves to the left closing switches 14 and 16.

When the thermostat moves to the left and causes contacts 3 and 4 toengage, no circuit will be closed since switch 16 is open but uponcontinued movement to the left contacts 6 and 8 will close to set up thefollowing circuit for initially energizing the relay coil 10; battery18, wire 20, bi-metallic element 2, contact 6, contact 8, wire 22, relaycoil 10, wire 24, and battery 18.

The energizing of coil 10 draws armature 12 to the left and closesswitch 14 to set up the following holding circuit for coil 10: battcry18, wire 20, bi-metallic element 2, contact 3, contact 4, wire 26,switch 16, wire 28, relay coil 10, wire 24, battery 18. Vibrationbetween contacts 6 and 8 will therefore not result in relay chatter forthe relay remains energized through its holding circuit. \Vhen contacts3 and 4 disengage the holding circuit will be broken and armature 12will move to the right and open switch 16. lie-engagement of contacts 3and 4 will thus not energize the relay and there will be no chatter uponvibration between these contacts. For purposes of illustration, armature12 has been shown as controlling a switch 14 in the energizing circuit30 of a motor 32.

It will be seen that elimination of chatter and proper operation dependsupon proper engagement of both pairs of contacts 3 and 4, and 6 and 8.If contacts 6 and 8 become corroded and fail to close properly, relaycoil 10 will never energize. If contacts 3 and 4 do not close properlythe relay will chatter upon vibration between contacts 6 and 8.

Referring now to Fig. 2, which illustrates asimple embodiment of theprinciples of the present invention, the numeral 40 designates abi-metallic element fixed at one end in a block of insulating material42 and carrying a contact 44 at its other end. A resilient metal strip46 which is mounted in an insulating block 48 at one end, is positionedopposite the bi-metallic element 40 and carries a contact 50 which isengaged by contact 44 upon movement of bi-metallic element 40 due totemperature change.

The relay coil 52 has an armature 54 which assumes a lowermost positionas shown when the coil is de-energized and is drawn upwardly when thecoil is energized. Armature 54 has a connection with the resilient metalstrip 46 to raise the same together with its contact 50 into theposition shown in dotted lines when the relay coil is energized.

If it be assumed that the thermostatic element 40 and the strip 46occupy the positions shown in full lines, and a change in ambienttemperature, for instance a temperature drop,

causes element 40 to move downwardly until contact 44 touches contact50, the following circuit for energizing relay coil 52 will be set up:battery 56, wire 58, bi-metallic strip 40, contact 44, contact 50, metalstrip 46, wire 60, relay coil 52, wire 62, battery 56. At the instantcoil 52 is energized, armature 54 will move upwardly and tend to movestrip 46 into the position shown in dotted lines. Preferably strip 46 ismore flexible than bi-metallic element 40 so that contact 50 will remainin approximately the position shown in full lines .even after it hasbeen engaged by contact 44 and the armature has moved to uppermostposition. If the temperature now rises and causes element 40 to moveupwardly, contact 50 will follow contact 44 due to the force exerted byarmature 54 upon strip 46 until the strip and contact reach the positionshown in dotted lines. When bi-metallic" element 40 finally movesupwardly a sutficient amount above the dotted line position of theresilient strip 46 to cause disengagement of contacts 44 and 50, theenergizing circuit for relay coil 52 will be broken and armature 54 willmove downwardly into the position shown whereupon resilient strip 46will also move downwardly into its full line position.

It will be observed that possibility of relay chatter is precluded bothupon initial energization of the coil and upon subsequentde-energization. The instant contacts 44 and 50 engage, the forceexerted upon resilient strips 46 by the armature will serve to hold themtogether until bi-metallic element 40 has moved backward an appreciableamount. There can thus be no vibration between the contacts at thistime. After the element 40 has moved contact 44 above the dotted lineposition of contact 50. the. latter contact will immediately drop backto its full, line position away from contact 44 thereby to precludevibration between the two. The arrangement allows opening and closing ofa relay circuit by means of a single pair of contacts without permittingchatter.

For purposes of illustration, the armature 54 has been shown ascontrolling the switch 64 which is in the energizing circuit 66 for anydesired load such as motor 68.

Referring finally to Figs. 3 and 4, where in the invention is shown asapplied to a time switch for periodically opening and closing theenergizing circuit for any desired load, numeral 70 designates a panelof slate or other insulating material upon which is mounted the fieldcore 72 of a relay having an energizing coil 74 and an armature 7 6which is pivoted at 78. When the relay is not energized, armature 7 6assumes the position shown and when the relay is energized it moves tothe left about its pivot 7 8 (Fig. 4). For purposes of convenience andclarity of illustration, the armature is shown in Fig. 3

as moving between a lower position assumed when the relay is notenergized and an upper position assumed and held while the relay isenergized. The armature carries c0ntacts 80 which engage contact 82 whenthe relay is open and engage contact 84 when the relay is closed,contacts 82 and 84 both being mounted on the panel.

A thermostatic element which in this case is a bi-metallic strip 86 ismounted on the panel 70 and is arranged to be heated by the heating coil88. Mounted opposite the bimetallic strip 86 is a second, similarbi-metallic strip 90 and the strips 86 and 90 carry oppositely disposedcontacts 92 and 94 respectively, which are spaced apart when strips 86and 90 are at the same temperature. Variations in ambient temperaturewill not affect the relative positions of contacts 92 and 94 for as onemoves down upon ambient temperature rise, for instance, the other willalso move down and compensate for the the change. If the strip 86 isheated to a higher temperature than strip 90 by means of the heatingcoil, however, it will move down a greater amount than strip 90 andcause contact 92 to engage contact 94.

The bi-metallic strip 90 is supported from a block 96 carried by a shortresilient strip 98 secured to a U-shaped bracket 100 which is fastenedto the panel 70. As a consequence, it is capable of resilient tiltingmovement about the middle of strip 98. The block 96 carries at its lowerend a long metal strip 102 and directly beneath it a short rigid bar104. The lower leg of the bracket 100 has a set screw 106 which engagesthe lower surface of rigid bar 104 so as to tilt block 96 to the leftand raise the outer end of himetallic strip 90 which carries contact 94.The setting of screw 106 therefore determines the distance betweencontacts 92 and 94 under ambient temperature conditions. By adjustmentof this set screw, the temperature difference necessary to causecontacts 92 and 94 to engage can be regulated and the time lapse betweeninitial heating of the coil 88 and the engagement of the contacts canthus also be regulated.-

The armature 76 carries a projecting lug or stop 108 which is out ofengagement with strip 102 when the armature is'in open position as shownin Fig. 4. When the relay is energized and the armature moves to theleft about its pivot 78 the lug 108 will engage the lower surface of theouter end portion of strip tilt block 96 upwardly to the right with theresult that the outer end of strip 90 carrying contact 94 will receivean upward force in the direction of bi-metallic strip 86 and contact 92.A set screw 110 which is mounted in the upper leg of the U-shapedbracket 100 passes through holes 112 and 114 in the bi-metallic strip 90and the metal strip 102 102 to raise the same and thereby to engage theupper surface of the rigid bar 104 and thereby limit the upward movementof contact 94 after the armature has closed.

\Vhen the coil 88 heats bi-metallic strip 86 sufficiently, it will movedownwards until contact 92 touches contact 94. Assuming that thearmature closes upon engagement of these contacts, lug 108 will exert anupward force on strip 102 with the result that contact 94 will receivean upward force pressing it against contact 92. If the temperature ofstrip 86 then falls it Wlll begin to move upwardly but contact 94 willfollow contact 92 until block 96 has tilted a sufiicient amount to causethe upper surface of rigid bar 104 to engage the lower end of set screw110. Upon continued upward movement of strip 86 the contacts willseparate, the relay will be de-energized with the result that lug 108will move away from metal strip 102, and contact 94, bi-metallic element90, block 96, rigid bar 104, and metallic strip 102 will,

drop down into the position shown in Fig. 4.

It will be noted that bi-metallic strip 86 is at a lower temperaturewhen the contacts separate than when they first engage and that thistemperature difi'erence can he regulated by means of set screw 110. Ifthe set screw 110 is adjusted so that its lower edge is very close tobar 104 when the parts are in the position shown in Fig. 4, for example,the outer edge portion of strip 102 will be raised the usual amountu'pon closure of the relay but the upward movement of bar 104, andconsequently of bi-metallic strip 90 and contact 94, will be limited bythe set screw. Thus the contacts will separate upon only very slightupward movement of strip 86 away from the position in which they firstengaged and it may be said that the contacts will separate when thestrip 86 falls to a temperature only slightly lower than that at whichthey first engaged. If the set screw 110 is raised, however, there willhave to be a greater temperai ture' fall on the part of bi-metallicelement 86 before the contacts will separate. Since the time necessaryfor the temperature drop required to effect separation of the contactsvaries with the amount of the drop, the set screw 110 further regulatesthe time during which the contacts are in engagement.

Upon inspection of the wiring diagram shown in Fig. 3, it will be seenthat when the contacts 92 and 94 are separated as shown, the relay isnot energized and heating coil 88 receives current through the followingcircuit: side of line 112, wire 114, heating coil 88, wire 116, contact82, contact 80, wire 118, and side of line 120. As current flows throughcoil 88 it will radiate heat and raise the temerature of bi-metallicstrip 86 with the res ult that its outer end will move downward carryingcontact 92 into engagement with contact 94 thereby to set up thefollowing circuit for energizing relay coils 74: side of line 112, wire.122, relay coil 74, wire 124, bi-metallic strip 86, contact 92, contact94, bi-metallic strip 90, wire 126, and side of line 120.

Vhen coil 74 is energized the armature 7 6 will close, pulling contact80 away from contact82 and into engagement with contact 84, and exertingan upward force on metal strip 102. Separation of contacts 80 and 82will break "the circuit for heating coil 88 so that it will immediatelybegin to cool and the closing of contacts 80 and 84 will close thefollowing circuit for any desired load such as a stoker motor, forinstance: side of I line 112, wire 128, motor 130, wire 132, contact 84,contact 80, wire 118 and side of line 120. As the coil 88 coolsbi-metallic element 86 will also cool thereby to raise contact 92 butcontacts 92 and 94 will not immediately separate due to the upward forcewhich causes contact 94 to remain in engagement until bimetallic element86 is at a temperature lower than that at which engagement was firstmade. At the instant of separation, contact 94 willoccupy a positionhigher than at the instant of engagement but will drop back as thearmature opens upon de-energization of the relay, into substantially theposition occupied at the instant of initial engagement. As the armatureopens, contact 80 will be moved into engagement with contacts 82 wherebythe motor circuit will be broken and the heating coil circuit againclosed. When the bi-metallic strip 86 again reaches a sufficiently hightemperature, contacts 92 and 94 will close, the heater circuit will bebroken, and the motor circuit will be closed and remain closed untilstrip 86 cools sufficiently to cause separation of contacts 92 and 94.

In operation the relay will be periodically opened and closed toperiodically operate the motor and it will be apparent that the timebetween openings and closings can be regulated by adjustment of the setscrews 106 and 110.

It will further be observed that there will be no opportunity for relaychatter. There can be no vibration between contacts 92 and 94 uponinitial engagement because of the upward force which presses themtogether the moment contact is made. Also there can be no relativevibration at the point of disengagement for the contact 94 will dropback an appreciable amount at the instant of separation.

I claim as my invention:

1. The combination with a relay having a movable armature and anenergizing circuit, of a pair of contacts controlling said circuit, amember movable in response to changes in a physical condition carryingone of said contacts, a second movable member carrying the other of saidcontacts in position to be engaged by the contact on said condition resonsive member upon relative movement of the latter, and means associatedwith the relay armature for exerting a force on said second movablemember in the direction of the condition responsive member when thecontacts initially engage, said force causing said second movable memberand contact to follow the condition responsive member and contact for alimited distance upon movement of the latter in a direction away fromits point of original engagement with the former, whereby said contactsseparate at'a point spaced from that at which they originally engaged.

2. The combination with a relay having a movable armature and anenergizing circuit, of a single pair of contacts controlling saidcircuit, a movable member carrying one oi said contacts and beingadapted to move it to and from the other in response to changes in itstemperature, resilient means supporting the second contact and adaptedto assume a normal position of rest, and means associated with the relayarmature for exerting a force on said resilient supporting means in thedirection of the temperature responsive member when the contactsinitially engage, said force causing the contacts to separate at a pointspaced from that of initial engagement upon movement of the temperatureresponsive member in a direction away from the original position of thesecond contact.

3. The combination with a relay having a movable armature and anenergizing circuit, of a temperature responsive bi-metallic stripcarrying a contact, a resilient strip carrying a second contact forco-operating with the first said contact to open and close the relayenergizing circuit, and means on said movable armature for exerting aforce on said resilient strip to move the second contact in thedirection of the first said contact when they initially engage toenergize the relay and move the armature, whereby said contactsdisengage at a'point removed from the point of engagement, the resilientstrip being adapted to move the second'contact away from the first upontheir separation and resulting movement of the armature to the positionit occupies when the relay is de-energized.

4. The combination with a relay having a movable armature and anenergizing circuit, of a single pair of contacts controlling saidcircuit, a bi-metallic strip movable in response to temperature changescarrying the first of said contacts, a resilient metal strip fixed atone end and being deformable from a position assumed when unrestrained,a block carried at the other end of the deformable strip, a second stripfixed at one of its ends to one end of the block and carrying the secondcontact on its other end at a point opposite the first contact, a thirdstrip fixed at one of its ends to the other end of said block, and meansassociated v'ith the armature of the relay for exerting a force on saidthird strip when the relay is energized.

5. The combination with a relay having a movable armature and anenergizing circuit, of a single pair of contacts controlling saidcircuit, a bi-metallic strip movable in response to temperature changescarrying the first of said contacts, a resilient metal strip fixed atone end and bong deformable from a position assumed when unrestrained, ablock carried at the other end of the deformable strip, a second stripfixed at one of its ends to one end of the block and carrying the secondcontact on its other end at a point opposite the first contact, a thirdstrip fixed at one of its ends to the other end of said block, a rigidbar lying adjacent said third strip and fixed to the same end of theblock, means associated with the armature of the relay for exerting aforce on said third strip when the relay is energized thereby to tiltthe block and the second contact in the direction of the first saidcontact, and a stop co-operating with the rigid bar to limit the tiltingmovement of the block.

6. The combination with a relay having a movable armature and anenergizing circuit, of a single pair of contacts controlling saidcircuit, a first thermally responsive member carrying the first of saidcontacts, a second thermally responsive member carrying the secondcontact at a spaced distance from the first contact when the thermallyresponsive members are at like temperatures, a heating coil for heatingthe first thermally responsive member, means for interrupting theenergizing circuit for said coil thereby to move the first contact intoand out of engagement with the second contact, and means associated withthe relay armature for exerting a force on the second contact in thedirection of the first when the relay is energized, whereby saidcontacts separate and break the relay energizing circuit at a pointdiiierent from that at which they initially engaged to complete it, uponmovement of the first contact away from the second.

7. The combination with a relay having a movable armature and anenergizing circuit, of a single pair of contacts controlling saidcircuit, a first thermally responsive member carrying the first of saidcontacts, a second thermally responsive member carrying the second ofsaid contacts, said contacts being spaced apart when the thermallyresponsive members are at like temperatures, a heating coil for heatingthe first thermally responsive member thereby to move the first contactinto engagen'ient with the second, an energizing circuit for said coil,a switch in said coil energizing circuit connected with the relayarmature, said switch being closed when the armature is in open positionand vice versa, and means associated with the relay armature forexerting a force on the second contact in the direction of the first andmoving the former upon retraction of the latter for a limited distance,whereby said contacts separate and break the relay energizing circuit ata point diiierent from that at which they initially engaged to com leteit, when the first contact moves away rom the second due to cooling ofthe heating coil.

8. The combination with a relay having a movable armature and anenergizing circuit, of a single pair of contacts control ing saidcircuit, a first thermally responsive member carrying the first of saidcontacts, a second thermally responsive member resiliently supported atone end and carrying the second of said contacts at its other end, saidcontacts being spaced apart when the thermally responsive members are atlike temperatures, a heating coil for heating the first thermallyresponsive member thereby to move the first contact into engagement withthe second, an energizing circuit for said coil, a switch in said coilenergizing circuit adapted to be closed when the relay is not energizedand open when it is energized, and means associated with therelayarmature for actuating the second thermally responsive member andcontact in the direction of the first thermally responsive member andcontact for a limit ed distance covered upon energization of the relayand retraction of the first contact from its original position ofengagement with the second contact an amount equal to said distance.

9. In combination, a relay having a movable armature, an energizingcircuit for the relay, a first member movable in response to temperaturechanges, a second member similarly movable in response to temperaturechanges, means for heating the first said member thereby to move thesame relatively to the second, a pair of contacts carried by saidmovable members and cooperating to open and close the aforesaidenergizing circuit upon movement of the first said member due to changesin its temperature set up by 7 said heating means, and means associatedwith the relay armature for actuating said second member in thedirection of the first upon energization of the relay.

In witness whereof, I have hereunto set my hand this 9th day of July,1931.

DANIEL G. TAYLOR.

